Project 1 will focus on the optimization of the next generation polyvalent Env HIV vaccine formulations using the multi-gene, polyvalent DMA prime - protein boost technology platform. Our first HIV vaccine formulation, DP6-001, was developed several years ago for a proof-of-concept trial to demonstrate the immunogenicity of the DMA prime - protein boost approach in human volunteers. The primary Env antigens isolated from HIV infected patients in mid-1990s were selected randomly based on their genetic clades. Rapid progress in the HIV vaccine field now provides us with a much larger selection of primary Env antigens, especially those Env proteins from clades less studied in the past and those Env proteins with more detailed information about the patients from whom the viruses were isolated. In addition, the recently developed pseudotyped neutralization assay and newly established target HIV-1 primary virus panel ("the Tiers System") provides a measurable standard to guide our selection of more relevant primary Env antigens for the development of HIV vaccines focusing on the induction of neutralizing antibody responses. By taking advantage of the above progress, we have identified a group of primary Env antigens that were able to elicit much broader neutralizing antibodies than those included in our previous formulation DP6-001. In the current Project 1 of this IPCAVD program, the following studies will be conducted: Aim 1 To finalize the selection of next generation polyvalent Env formulation to further improve the quality of neutralizing antibody activities. Aim 2 To select an immunogenic adjuvant to be used as part of the protein boost for the next generation polyvalent Env formulation. Aim 3 To test the immunogenicity of next generation polyvalent Env formulation when the DMA priming is delivered by the electroporation method. Aim 4 To examine the epitope profiles in immune sera elicited by DMA prime-protein boost approach and identify the epitope specificities of antibodies responsible for the neutralizing activities.